1. Field of the Invention
The present invention relates to a fuel cell system that generates electric energy through electrochemical reactions and a control method thereof.
2. Description of the Related Art
A Fuel cell system supplies a fuel gas, such as a hydrogen gas, and an oxidizing gas containing oxygen to a fuel cell to cause these gases to electrochemically react with each other through an electrolyte of the fuel cell in order to obtain electric energy.
A fuel cell system of the related art is provided with a hydrogen concentration sensor on an anode off-gas passage through which an anode off-gas discharged from the fuel cell passes, and measures the concentration of hydrogen contained in the anode off-gas (see Japanese Patent Application Publication No. 2004-95300 (JP-A-2004-95300), for example).
The hydrogen concentration measured by the hydrogen concentration sensor is used to perform various control operations of the fuel cell system, such as regulating the amount of the anode off-gas discharged from the anode side of the fuel cell. The hydrogen concentration sensor is therefore required to have high measurement accuracy. However, the accuracy of the hydrogen concentration sensor can decrease as it is used for a long time, which can cause an error.